Oxygen evolution and photosynthetic energy storage during the cell cycle of green alga Scenedesmus armatus characterized by photoacoustic spectroscopy

The photosynthetic activity of Scenedesmus armatus, synchronized by light/dark regime of 14/10 hours, was characterized using the photoacoustic (PA) spectroscopy technique. Frequency-dependent analysis of the PA signal was carried out to separate its photobaric and photothermal components. The photochemical energy storage (ES) measured at a high frequency of 180 Hz and the efficiency of oxygen evolution measured at a low frequency of 4 Hz were found to have different runs during the light phase (14 h) of the cell cycle. ES changed from 27 percnt; for young autospores illuminated for 0.5 h to 35 percnt; for mother cells starting to release the next generation of autospores. The efficiency of oxygen evolution rapidly increased, reaching the maximum value in 3-4 h, and next gradually declined with time during the cell cycle. The time of the photothermal component of the PA signal creation measured in a PA cell changed from 1.63 to 1.87 ms. The coefficient of oxygen diffusion through the cell wall was 7.84 · 10−7 cm2 s−1. In view of a very good correlation between the PT signal and the cell volume during the cell cycle, the PA technique can also be employed to monitor the growth of cells or biomass production.